Excellent place and highly recommended. The apartment is located in a sub Soi off of Soi Thong Lo, an area of BKK that is filled with pubs, restaurants, etc. with something for everyone.
Location is great - far enough back from the main road that traffic noise is minimal, but close enough to all the "action". 24 hour grocery is steps away, a variety of restaurants close by, etc. The BTS is about a km away. A bit of a walk on a hot day, but regular taxis (~ 40 baht) are available, moto taxis (~20 baht) are numerous, and there is a soi bus that runs up and down for even cheaper.
The apartment itself is cozy, but perfect for 1-2 people. Well furnished and stocked. Bed was good and the room was dark if you wanted to sleep in. Internet was fast, allowing needed work to be done. Nice touch was a smart TV which allowed access to Netflix, etc. Full size fridge was nice. Did not do any cooking, but there is a 2 burner cooktop available. Nice sized shower in the bathroom. Water pressure and hot water were fine.
The rooftop pool is just okay. The pool has absolutely zero shade (umbrellas or otherwise), which in the heat and sun of BKK can be a bit of a problem. Never saw it being used. The fitness center is relatively small, with some cardio machines, etc. Never busy however.
Khun Natthapol is a great host. Quick, accurate communication and ready to respond to any questions. Very accommodating to my early early morning check in. Everything was smooth in my communications with him.
All in all, I would highly recommend this place. Great value, great location, great apartment. Will definitely look to stay here again my next time in BKK.